Macroscopic Characteristics and Formation Mechanisms of Arctic Clouds Based on CloudSat-CALIPSO Data

On the basis of CloudSat-CALIPSO (CloudSat-Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite inversion data and ERA5 (ECMWF Reanalysis v5) monthly average reanalysis data, the temporal and spatial distributions of the total cloud amount and stratocumulus clouds (Sc) with the highest frequency in the Arctic are analyzed, and the possible reasons for the formation of Sc are discussed. The results show that the total cloud amount in the Arctic region is the largest in autumn, and the increase in cloud amount is more obvious in the Kara Sea–Chukchi Sea region. Factors such as the relatively large sea–air temperature difference, strong upward movement of the boundary layer forced by the surface latent heat flux, and high relative humidity are the main causes of cloud formation and maintenance in this area. In addition, a large amount of Sc is observed in the Arctic, mainly in the Norwegian Sea–Barents Sea, which is almost without sea-ice cover all year round. The lower tropospheric stability (LTS) in this area is negatively correlated with the amount of Sc. The greater the LTS is, the smaller the amount of Sc. This phenomenon is different from what is observed in tropical, mid-latitude regions. The factors affecting the formation of Sc in this sea area can be attributed to the open ocean reducing the LTS through surface–atmosphere coupling and the turbulent surface flux of heat and humidity, which promote the formation of Sc and increase the coverage of Sc.